Rare monster bug

Just came across a monster that had:

Lightning mirages when hit
Regenerates life
Extra Energy Shield
Conjures Flamewalls
Siphons Mana and Deals Lightning Damage

Killed me in less than 2 seconds. Im not even sure what killed me because there was no flamewall or lightning mirages up but my life was being siphoned at the same time that my mana was even though thats not a modifier. Still had 4 or 5 rares to kill so ruined that whole map.